Method for consolidating material



United States Patent METHOD FOR CONSOLIDATING MATERIAL Herbert C.Walther, David A. Kuhn, and Derry D. Sparlin, Ponca City, Okla,assignors to Continental Oil Company, Ponca City, Okla, a corporation ofOklahoma No Drawing. Filed June 6, 1962, Ser. No. 200,310

11 Claims. (Cl. 166-33) This invention relates to a method ofconsolidating loose or incompetent subterranean formations. Moreparticularly, the invention relates to improvements in methods forconsolidating incompetent, subterranean formations, which methods employa resinous composition as a consolidating agent.

In the production of subterranean fluids, such as oil, gas, water, etc.,a number of difliculties are encountered when the well by which thefluids are produced penetrates a loose or unconsolidated subterraneanformation. Such formations frequently are composed of loose water or oilsands, and the grains of the sand become entrained in the fluid beingproduced to be carried into the well bore. The result of suchentrainment, among other things, is the abrasion of the pumpingequipment in the well bore, the clogging of strainers, and the sandingin of the cavity immediately adjacent the strainer. These results inturn ultimately cause a sharp decrease in the rate of production andhigh maintenance costs.

In an effort to reduce the deleterious results generally associated withproducing fluids from a unconsolidated formation, it has heretofore beenproposed to inject an age-hardenable cementing agent into the producingformation adjacent the well bore in order to consolidate or make rigidthe formation. The cementing agent directly contacts the loose grains orparticles in the formation and, by bonding them to each other, reducestheir mobility.

One of the cementing agents widely used in such pre .vious processes,and also in the instant process, is a resin forming compositioncontaining formaldehyde, phenol, and a suitable catalyst. In oneconsolidating method, this composition, in liquid form, is pumped downthe well bore and into the formation where it sets up to a hardenedstate upon standing. A variety of means is employed for flushing theexcess resin from the formation so that the permeability of theformation is retained.

As evidenced by the substantial number of relatively recent innovationsand modifications which have been developed in the basicphenol-formaldehyde resin process, this method of formationconsolidation does not as yet afford an entirely statisfactory solutionto the difficulties associated with unconsolidated formations. One ofthe problems which has not been solved to the most desirable degree isthat of obtaining a strong or tenacious bond between the resinousmaterial and the particles of sand or other particulate materials in theformation. As a result, effective consolidation is often not achieved.

One of the efforts .to improve the tenacity of the bond which isestablished between the formation particles and the resin is describedin U.S. Patents 2,378,817 and 2,604,172 to Gilbert G. Wrightsman, whichconsists primarily of introducing into the formation an agent capable ofrendering the formation particles wettable by the resin-forming liquid.Although a substantial improvement in the uniformity and tenacity of thebond which is established between the resin and formation particlesresults from use of this technique, the strength of such bond is stillfar lower than optimum.

One aspect of the present invention concerns a novel and practicalmethod for consolidating loose or incompetent formations of the typedescribed, which results in a strong, tenacious bond between a resinousmaterial which is pumped into and set up in the formation, and thegrains of material composing the formation.

By the use of the invention, the compressive or crushing strength ofconsolidated silicious materials may be greatly enhanced as compared tothe crushing strength obtainable by employing any of thephenol-formaldehyde consolidation methods heretofore in use. Moreover,the method of the invention does not result in any serious reduction information permeability.

In one of its broader aspects, the invention resides in the use ofcertain types of chemical compounds to chemically couple, or bond,agehardenable resin molecules to impart great rigidity and strength tothe consolidated formation.

In general, the coupling agents which are employed have a molecularstructure which is (a) characterized by having a first functional grouplocated at an exposed position in the molecule for reacting with theresinous material which is used for consolidating the formation, and (b)is further characterized in having a second functional group, or anatom, located at a second exposed location in the molecule forestablishing a chemical bond with the granular material of theformation. The coupling agent thus provides a strong chemical bridgelinking the molecules of the consolidating resinous materials to thegrains of material in the formation.

Coupling agents of the general type described include, but are notlimited to, Werner-type co-ordination compounds consisting of transitionmetal salt complexes of alpha, beta unsaturated acyclic carboxylicacids, particularly the cobalt, chromium, zinc, and nickel complexes,and organo-functional silanes, such as 'y-aminopropyltriethoxysilane,and 6-aminobutylmethyldiethoxysilane. Other specific examples of theseand other types of suitable compounds Will appear hereinafter.

In one method of practicing the process of the present invention, theformation to be consolidated is first isolated by means well-known inthe art, such as, by packers. A quantity of diesel oil or other inerthydrocarbon material, such as distillate or crude oil, is then injectedinto the formation to flush out the formation and cleanse the formationparticles. A solution or mixture containing the coupling agent is nextinjected into the formation together with, in some instances, a pluggingretardant. This step is followed by the injection into the formation ofa liquid to remove excess coupling agent. Then follows a resin treatmentwhich comprises the steps of injecting a volume of a resin mixture intothe formation, removing the excess plastic material from the intersticesbetween the formation particles by flushing with an inert flushingmaterial, and finally shutting in the well to maintain a staticcondition within the formation for a sufficient period of time to permitthe plastic to set up to a hardened state.

While the above brief description presents a preferred method ofpracticing the invention, certain deviations in this process may be madewithout departing from the spirit of the invention. For example, thecoupling agent may be added directly to the resin mixture in onealternative, or the coupling agent may be incorporated into theoverflush and placed in the formation after the resin has been injected,as a second alternative.

By the described process, the state -of formation consolidation isvastly improved in that a more rigid, tenaciously interconnectedstructure is formed without decrease in formation porosity to adetrimental degree. The crushing strength of the consolidated formationmaterials is generally increased by a factor of at least 5, and thepermeability of the formation is ordinarily decreased by not more than35 percent, and usually substantially less.

From the foregoing description, it will be apparent that it is a majorobject of the present invention to im- U a prove presently usedprocesses of consolidating incompetent formations wherein anage-hardenable plastic or resinous material is injected into the looseformation to harden.

It is a more specific object of the invention to improve the methods nowin use for rendering compentent, loose or unconsolidated formations fromwhich a fluid is being produced, which methods utilize aphenol-formaldehyde resin as the consolidating material. The basicprinciple underlying the invention may,- however, be employed when othertypes of organic resins, such as urea, melamine, polyester, and acrylic,are used.

Another object of the invention is to increase the permanency and degreeof consolidation effected by artificial means in a porous,fluid-producing formation.

A further object of the present invention is to impart a higher crushingor compressive strength to an artificially consolidated subterraneanformation than has heretofore been possible using methods previouslyknown.

Another object of the invention is to improve the strength anddurability of the porous skeletal structure of an artificiallyconsolidated subterranean formation without seriously decreasing thepermeability of the formation.

Another object of the invention is to provide an improved practicalprocess for consolidating incompentent subterranean formations, whichprocess is sufiiciently simple in nature to permit it to be practicedrelying largely upon consolidating techniques heretofore known andappreciated.

A further object of this invention is to provide a practical process forconsolidating incompetent subterranean formations wherein an amount ofoverflush is not critical.

A more specific object of the present invention is to provide animproved process for consolidating incompetent subterranean formationsusing a partially polymerized resin mixture.

Other objects and advantages of the invention will become apparent asthe following detailed description of the invention is read.

Before describing in greater detail one series of steps entailed in theprocess of the invention, the coupling agents which are employed inpracticing the process and the mechanism by which they act in forming achemical bridge between the silicious material in the formation and theconsolidating resinous material will be discussed. Typically, suchcoupling agents will comprise molecules having a group or atom which iscapable of reacting with, or being strongly held by, the formation sandsand having a reactive organic group which orients outwardly from thesand and is capable of combining with the consolidating mate-rials.Molecular species of this general type include Werner complex-typecompounds in which the multivalent transition metals, preferablychromium, cobalt, nickel, copper, lead, and zinc, are co-ordinated witha carboxylic acido group; vinyl-trichlorosilanes; and certainarninoalkylethoxysilanes. Preferred in the latter group of compounds arethose in which at least one of the alkyl substituents of the siliconatom is at least 3 carbon atoms in chain length so that the amino groupwhich at attached to the terminal carbon atom of such alkyl group islocated no closer to the silicon atom than the gamma position. 7-, 6-,and e-aminoalkylethoxysilanes are also satisfactory as are higherhomologues of these materials having extended alkyl chains attached tothe silicon atoms, with the amino group bound to the terminal carbonatom of such extended alkyl chains.

Of the Werner complexes employed, those containing an alpha, betaunsaturated acyclic carboxylic acido group containing from two to sixcarbon atoms in the alpihatic chain, such as acrylic acido andsubstituted acrylic acido groups, are preferred. Among other acid typeswhich may be used are sorbic acid, crotonic acid, propionic acid, vinylacetic acid, alyl acetic acid, oleic 'acid, maleic acid, and adipicacid. Chromium and cobalt are the preferred metals of the complex.

In addition to and in some cases complementary with the above generaldiscussion of the characteristics of coupling agents which may be usedin the present invention, a number of types of chemical structuralformulas have been recognized as being suitable for use in the process.In many of the following structural examples, the symbol X will appearand will be identified as an anion. For further clarification, whichneed not be repeated in each of the individual examples, it should bestated that any anion is contemplated by X. Generally, however, Br, Cl,F, I, (NO and (C10 are preferred. For convenience and reference, thesestructural-type formulas will be set forth hereinafter in numberedorder. Water bound in the co-ordination shell is not shown.

(1) 1,2-diamines and transition metal ions.

wherein:

R: (CH CH=CH or OH (a=05) X=an anion M=Ni Cu Zn, Cd Cr or Co n=1 or 2m=2 or 3 The following specific structural example of3,4-diaminobutene-l-tetraaquocobalt (III) chloride is typical ofcompounds of this type:

t/ H2C=OHOH-N C0013 CHz-IIT\ Diaquobis(phydroxyphenylethylenediamine)chromium (III) perchlorate andbis(3,4-diaminobutene-1)diaquochromium (III) chloride are furtherexamples of compounds which typify this group of coupling agents.

(2) Substituted salicylaldehydes and transition metal ions.

wherein M=Mn Fe C0 Ni Cu Zn Cd Pb Cr or m=1 or 2 The following specificstructural example of bis(2,4- dihydroxybenzaldehydato)diaquochromium(III) chlo ride is typical of compounds ofthis type:

HO CrOl Bis(2 hydroxy 4 aminobenzaldehydato)diaquo chromium (III)chloride; 2,4-dihydroxybenzaldehydatos tetraaquocobalt (III)perchlorate; and 2-hydroxy-4- aminobenzaldehydeatodiaquonickel (II)nitrate are further examples of compounds which typify this group ofcoupling agents.

(3) fl-Diketones and transition metal ions.

OI (CH2) cH=CH2, 01' (CH NH (a=O5, -b=15 X=an anion M=Mn Fe Co Ni Cu ZnCd Co Mn or Cr n=1 or 2 m=1 or 2 The following specific structuralexample of bis(6-heptene-2,4-dionato)diaquochromium (III) nitrate istypical of compounds of this type:

The following specific structural example of 3-aminomethyl-2,4-pentanedionatodiaquonickel (II) chloride is typical ofcompounds of this type:

Bis(3 hydroxyphenyl 2,4 pentanedionato)diaquocobalt (III) chloride;bis(1-hydroxyphenyl-2,4-pentanedionato)diaquochromium (III) nitrate; andl-hydroxyphenyl 2,4 pentanedionatotetraaquochromium (III) nitrate arefurther examples of compounds which typify these groups of couplingagents.

(4) a-Aminocarboxylic acids and transition metal ions.

wherein:

CH2, OI

X=an anion M=Mn Fe C0 Ni Cu Zn Cd Co or Cr m: 1 or 2 n=1 or 2 Thefollowing specific structural example of bis(tyrosinato)diaquochromium(III) nitrate is typical of compounds of this type:

C CrNO:

Bis(lysinato)diaquoco-balt (III) chloride; tyrosin-atoteraaquochrornium(III) chloride; and tyrosinatodiaquocopper (II) nitrate are furtherexamples of compounds which typify this group of coupling agents.

(5) a-Hydroxycarboxylic acids and transition metal ions.

b: 1-5) X=an anion M=Mn Fe C0 Ni Cu Zn Cd C0 Cr The following specificstructural example of p-hydroxyphenyllactatodiaquonickel (II) chlorideis typical of compounds of this type:

o NiOl 0 0 p-hydroxyphenyllactatotetraaquochromium (III) chloride anda-hydroxy-fi-aminopropionatodiaquocopper (II) nitrate are furtherexamples of compounds which typify this group of coupling agents.

(6) S-hydroxyquinolines and transition metal ions.

wherein:

R: OH, or -(CH NH or -(CH CH=CH (a X=an anion M=Co Ni Cu Zn Cr or Co m=1or 2 n=1 or 2 The following specific structural example ofbis(6-hydroxy-8-quinolino1a-to)diaquocobalt (III) chloride is tynical ofcompounds of this type:

HO /o '7 Bis( 6 amino 8 quinolinolatoadiaquochromium (III) chloride;bis( amino 8 quinolinolatodiaquochromium (III) chloride; and5-vinyl-8-quinolinolatodiaquonickel (II) nitrate are further examples ofcompounds which typify this group of coupling agents.

(7) Schilf bases of salicylaldehyde and transition metal wherein: R=OHor (CH ),,NH or (CI-I CH=CH -(a=15) X=an anion M=Cu Ni C0 Fe Zn Cr or CoThe following specific structural example ofsalicylaldehyde-p-aminophenyliminatodiaquocopper (II) nitrate is typicalof compounds of this type:

Bis(salicylaldehyde p hydroxyphenylirninatodiaquochromium (III) chlorideand salicylaldehyde-m-aminomethylphenyliminatotetraaquocobalt (III) perchlorate are further examples of compounds which typify this group ofcoupling agents.

(8) Silyl e-thers with functional groups which will bond to the plastic.

wherein:

or(CH CH CH or The following specific structural example of'y-aminopnopyltriethoxysilane is typical of compounds of this type:

Methyl-,S-aminoethyldimethoxysilane and dimethyl-B-(p-hydroxyphenyl)ethylethoxysilane are further examples of compoundswhich typify this group of coupling agents.

-terial and the sili-cious formation materials.

The chromium complex establishes a chemical bond through the chromiumatoms with the negatively charged silicious surfaces of the formationparticles. A chemical bond may then be formed between the methacrylatogroup and the methylene groups of the phenol-formaldehyde resin. Thechemical bridge formed may thus be portrayed schematically:

Resin I Sand OH I 011 E O Cr--OSi OH: OH I CH2CH1 o-Er-o si Theaminoalkylethoxysilanes which may be used as coupling agents alsoestablish chemical bridges interlinking the molecules of the resinousconsolidating ma- Thus, 7- aminopropyltriethoxysilane, which is apreferred composition in this process, reacts with the aldehydic groupof the phenol-formaldehyde resinous composition to form a'y-azomethinepropyltriethoxysilane, and the silicon atom of the silanolgroup bonds through oxygen to the silicon atoms of the formationmaterial.

Turning now to a description of one method of practicing the process ofthe present invention, the initial step performed is the preparation ofthe formation for the injection thereinto of one of the above-describedcoupling agents by injecting a relatively small volume of diesel oil orother inert, neutral liquid flushing agent into the formation to cleanthe surfaces of the sand particles. This enhances the ability of thecoupling agent to bond to the sand. The exact volume of flushing liquidwhich is injected will of course depend, among other things, on thethickness and porosity of the formation being treated but will usuallybe from .5 to 20 barrels per vertical foot of perforated formationinterval to be treated; there is, however, no criticality to the amountof preflush used.

Following the initial cleansing operation, a composition, includingcoupling agent of the type described and a suitable carrier, isintroduced into the formation. The carrier will vary considerably,according to the type of coupling agent utilized and the prevailingformation conditions, 'but in any case is characterized by being asolvent for the coupling agent and by being relatively inert with regardto the other constituents used in the process and to the formation.

A variety of compounds may be employed as a carrier for the couplingagent. For example, diesel fuel, water, cnude oil, distillate,isopropanol, etc., may be used, depending upon the economics andconvenience of a given situation and the coupling agent employed.Usually, however, diesel fuel will be a preferred carrier.

Usually the coupling agent will be from about 0.005 percent to about 10percent of the total composition with a preferred range of from about0.05 :percent to about 1.0 percent.

When the methacryl-ato chromic chloride coupling agent is employed, thenormally acid complex is preferably adjusted with a nitrogen-containingbase such as ammonium hydroxide to an initial pH of at least about 4.0,but not greater than about 7.0. It has been experimentally determinedthat an aqueous solution containing about 20 parts by volume of anisopropanol methacrylatochromic chloride solution (6 percent chromium),about 100 parts by volume of water, and about 4.4 parts by volume of a 1percent aqueous ammonia solution gives good results in water-saturatedloose sand strata. When using -aminopropyltriethoxysilane andE-aminobutylmethyldiethoxysilane as coupling agents, these compounds areusually made up from about 0.005 to about 10 percent aqueous or dieseloil solutions prior to injection into the formation. Generally, apreferred solution range is from about 0.05 to about 5 percent and anoptimum range from about 0.05 to about 1 percent. As in the case of thetotal volume of liquid used to flush out the formation initially, thevolume of coupling agent which is utilized will depend, among otherfactors, on the porosity, composition, and size of the formation beingtreated. Generally from about .2 to about 20 barrels of coupling agentsolution .per vertical foot will be used, although a preferred range isfrom about .5 to about 5 barrels.

After pumping the coupling agent into the formation, a second quantityof the inert, neutral flushing agent is usually injected into theformation to speed out and disperse the coupling agent. Generally about.5 to about 5 barrels per vertical foot of formation will be used forthis purpose, although as much as or more barrels or sometimes nooverflush may be used.

Next follows the introduction of the consolidating resinous material,usually in a suitable solvent, into the formation. In general, this maybe accomplished by any of the known and widely practiced techniques nowin use. Also, although the preferred resinous material to be used forconsolidation is a phenol-formaldehyde type, other resins of thethermosetting type, such as alkyd resins and acrylic resins, aresuitable. such resins and methods of introducing them to incompetentformations, reference may be made to U.S. Patent 2,378,817, issued toWrightsman et al., U.S. Patent 2,604,172, issued to Wrightsman, U.S.Patent 2,823,753, issued to Henderson et al., U.S. Patent 2,981,334,issued to Powell, and U.S. Patent 2,476,015, issued to Wrightsman. Inthe case of the phenol-formaldehyde resinous materials, anunpolymerized, or preferably a partially polymerized, mixture of phenoland formaldehyde which includes a suitable catalyzing agent, such as anaqueous caustic solution, is pumped down the borehole and out into theformation. The amount of consolidating material used will depend on avariety of parameters, including well geometry, formationcharacteristics, etc. Ordinarily, the amounts used in the instantprocess will coincide with the amounts used in the standardphenolformalde'hyde process. Thus, (generally, about .5 to about barrelsper vertical foot of perforated interval will be used, although apreferred range is from about .5 to about 5 barrels.

Immediately after the resinous composition is injected into theformation, the formation is again flushed with an inert, neutralmaterial to remove excess resinous material and prevent the pores of theformation from becoming clogged. The amount of overflush may varywidely, depending upon among other things the amount of polymerizationthat has taken place in the resin when it is injected. Generally, for anunpolymerized resin, less than about one barrel per foot of perforatedinterval will b-e'used, while in the case of a partially polymerizedresin mixture from no overflush to 10 barrels per perforated foot may beused, although in the latter case the amount of overflush is notcritical and substantially more may be used.

As examples of When the coupling agent is incorporated in the overflush,the ratio of coupling agent to carrier and the total amount of overflushmaterial used are the same as the ratios and amounts utilized when thecoupling agent is injected as a preflush. Similarly, when the couplingagent is added to the resin mixture before injection, the total amountof resin mixture used will be the same amount which would have been usedhad the coupling agent been injected separately. In this case, the ratioof coupling agent to resin mixture will be the same as the ratio ofcoupling agent to carrier when the latter mixture is injected prior tothe resin. As will be obvious to one skilled in the art, several of thecoupling agents listed herein may, when used in higher concentrations,be expected to accelerate polymerization rates beyond optimum limits.Consequently, before practicing the invention with the higherconcentrations, it may be found advisable to conduct a series ofreaction rate tests using standard laboratory techniques in order todetermine the optimum ratio between coupling agent and resin mixture for:a given situation.

Finally, the well is shut in, or at least flow is restrictedsubstantially, so that the consolidating material will have anopportunity to set up to a hardened state. As will be appreciated bythose skilled in the art, such settingup time may range from about 12 to48 hours, depending upon the resinous mixture employed and formationconditions.

As a preferred embodiment of the present invention, it has beendiscovered that the injection at the wellhead of a partially polymerizedresin mixture gives results superior to those obtained when anunpolymerized resin mixture is used. As used herein and in the appendedclaims, the phrase partially polymerized resin mixture is used toindicate those mixtures wherein reaction or condensation has begun butwherein polymerization has not reached an end point. These mixturesconsist essentially of one or more of the following classes of compoundsor elements: monomers, the initial reaction or condensation product ofthe monomers, prepolymers, and the final polymerization product.Moreover, the term polymerization as used herein is intended to includecondensation reactions as well as the more narrowly definedpolymerization processes.

It has been found that, when a partially polymerized phenol-formaldehyderesin mixture is introduced at the wellhead, the amount of overflushused after the injection of the resin into the formation becomes lesscritical. For instance, when an unpolymerized resin is injected, theamount of later overflush must be controlled within narrow limits tomaintain the advantages of the instant process. If too much overflush isused, the resin is washed from the critical portions of the formationwith a resulting decline in crushing strength. When, however, theinjected resin is partially polymerized, excess amounts of overflush maybe used without this deleterious effect.

This phenomenon occurs over a wide range of degrees of partialpolymerization, and it is believed that any significant amount ofpolymerization prior to injection at the wellhead will result in adecrease in the criticality of the amount of overflush later used. Inpractice, it is ordinarily preferred to allow polymerization to progressat least to the stage whereat the viscosity of the resin mixture isabout 1.25 times the original viscosity of the mixture. The originalviscosity will, of course, vary over a wide range, depending upon avariety of factors which will be obvious to one skilled in the art, notthe least of which is the identity of the initial reactants orcondensates. Generally, this range will vary from about 0.1 to about 10poises, although under extreme conditions of temperature, etc., theinitial viscosity may fall outside this range.

Beyond the minimum polymerization discussed above, resin mixtureswherein substantial polymerization has taken place may also be used,with a corresponding de crease in the criticality of the amount ofoverfiush. The limiting factor in the amount of polymerization of whichadvantage may be taken appears to be the pumpability of the solutioncontaining the partially polymerized resin mixture. Thus, so long asexisting equipment is capable of injecting a solution containing thepartially polymerized resin mixture into the formation, the upper limiton degree of allowable polymerization has not yet been reached.Generally, practical considerations preclude the use of a resin mixturewherein the partial polymerization has advanced to a point whereat thesolution evinces a viscosity much above about 25 stokes.

Experience has indicated that substantially optimum conditions arereached when the partially polymerized resin mixture has polymerized tothe point at which it is insoluble in diesel oil. At this point, theviscosity of the partially polymerized resin mixture is not such that itwill place undue strain on the wellhead equipment, while at the sametime relative large volumes of overfiush may be subsequently usedwithout washing significant amounts of the resin from the portion of theformation adjacent the well bore.

Aside from the optimum conditions mentioned above, a generally preferredrange of degrees of polymerization is from the degree of polymerizationat which the partially polymerized resin mixture becomes insoluble indiesel oil to the degree of polymerization which results in the solutioncontaining the partially polymerized resin mixture having a viscosity ofabout 25 stokes.

The following examples will serve to illustrate methods of employing theinvention. In many of these examples, there are a number of steps whichare repeated several times; and for purposes of brevity, these stepswill now be described in detail. Later they will be mentioned only byreference in the specific examples wherein the steps were carried out.

In each of the examples, sand cores were prepared using a Black Hawk Esand, which is a clean, white, silicious sand having particles rangingin size from about 60 mesh to about 325 mesh. Generally, the averagesize of the particles is about 100 mesh. The cores were prepared byacking a quantity of loose Black Hawk E sand under water into aresilient sleeve. A small quantity of 2040 mesh clean silicious sand wasplaced in each end of the sleeve followed by a 60 mesh screen.Subsequently, apertured plugs were placed on each end of the sleeve toform an essentially cylindrical core.

The sand consolidation treatments which are reported in the exampleswere evaluated in the laboratory by treating the cores under simulatedsubsurface conditions. In simulating these conditions, a core was firstplaced in a pressure bomb which was in turn immersed in a constanttemperature bath of about 160 F. A hydraulically simulated overburdenpressure of about 750 psi. was applied externally of the sleeve in whichthe sand sample was contained and, because of the resiliency of thesleeve, was transmitted substantially undiminished to the sand itself.In addition, provision was made for raising the temperature of testfluids to about 160 F. before they were flowed through the sand cores.

Prior to treatment of the cores or measurement of any core parameters,the cores were flushed with 10,000 to 20,000 cc. of No. 1 diesel fuel,hereinafter called diesel oil, to obtain irreducible water saturation.

In these experiments where permeability was determined, it wasdetermined by measuring the diesel oil flow rate and the pressure dropacross the core. Data obtained from these two variables were used indetermining permeability by mathematical relationships well known in theart.

In many of the following examples, reference will be made to a standardphenol-formaldehyde resin treatment. This standard treatment utilized aphenol-formaldehyde resin prepared substantially in accordance with theprocedures outlined in Examples 2 and 3 in U.S. Patent 2,981,334 and wasaccomplished in the following way: About cc. of a solution consisting ofapproximately 30 percent phenol-formaldehyde resin solids andapproximately 70 percent ethanol was pushed through a core, togetherwith approximately 0.9 cc. of a 25 percent aqueous NaOH solution byabout 100 cc. of diesel oil. Following the flushing with the resin, thecore was left in the constant temperature bath at F. for from three tofive days to allow the resin to harden and consolidate the sand core.After curing, the consolidated core was removed from the sleeve and cutinto 'Vr-inch lengths for further tests.

Example 1 Initial Percent Average Perrne- Return Crushing Core abilityPerme- Strength (Darcies) ability After 5 Days From the above results,it is at once apparent that there was a substantial increase in thecrushing strength of the cores treated 'by a coupling agent. Moreover,it would appear that, when relatively small amounts of the couplingagent are passed through the cores, plugging is not a major problem.

Example 2 Example 1 was repeated substantially except that methacrylatechromi e chloride was substituted for the 'y-aminopropyltriethoxysilane.The sand used in the cores had a slightly different size distribution.Results of permeability and compressive strength runs on these fourcores were as follows:

Percent of Compressive Retained Core Strength, Permeability p.s.i. AfterTreatment Standard Treated Core A 112 76 Standard Treated Core B 122 77Coupling Agent Treated Core C-.. 898 74 Coupling Agent Treated Core D823 68 The original permeabilities of all cores were the magnitude of8-l0 darcies. Thus, the maximum loss of permeability of 32 percentsustained by the second coupling agent treated core does not represent aserious or intolerable reduction in permeability. In fact, theemployment of the coupling agents appears to cause only a slightadditional loss of permeability when a normal amount of the couplingagent is flowed through the core.

In the preceding examples, attention has been given to the generalproblem of consolidating incomponent formations and to the solution ofthis problem. Thus, far, no mention has "been made of the fact thatunder some circumstances, for instance when relatively low permeabilityformations are involved, formation plugging may become a problem. Whilethis will not always occur, it is a pos sible complication when theconsolidation techniques discussed above are employed. Moreover, whenconsolidation is carried out through perforations in the well bore,-

which is usually the case, the portion of the formation immediatelyadjacent these perforations will receive a larger throughput than willthe other portions of the formation. It has been observed and willshortly be demonstrated that, as increasing amounts of coupling agentare flowed through the formation, plugging becomes of increasingimportance.

It has been discovered that plugging problems encountered in formationtreating of the type described above may be substantially lessened and,in some cases, obviated by the use of a plugging retardant which ischaracterized as being a solvent for both the carrier and the couplingagent. Examples of suitable plugging retardants are the fluid alcohols,such as butanol, hexanol and isopropanol; ketone-s, such as acetone,diacetone, .and methyl ethyl ketone; and esters, such as B-ethoxy ethylacetate and fi-met-hoxy ethyl acetate. Of these, isopropanol and acetoneare the preferred compounds. In practice, moreover, isopropanol willmost usually be chosen, inasmuch as it might also be expected to 'reducehydrolysis and, further, inasmuch as it has a sufliciently high flashpoint to reduce the danger of combustion at the wellhead.

In use, the plugging retardant is usually combined with the carrier,usually diesel oil, and the coupling agent. The ratio of pluggingretardant to carrier may be from about 2 percent to about 100 percentretardant, with a preferred range of from about 15 percent to about 35percent plugging retardant. The same ratios of coupling agent to carrieras described above are maintained.

The solution containing the plugging retardant is used in the manner andin the amounts described above for the complexing agent solution; thatis, broadly speaking, it is used as a prellush prior to the introductionof the consolidating agent into the formation.

The following examples maybe relied upon to show the effectiveness ofthe plugging retardant in the described process.

Example 3 Two sand cores were prepared as described previously, and oneof the cores was preflushed with 4,300 cc. of a 0.2percent solution of'y-aminopropyltriethoxysilane in diesel oil. The permeability measuredafter the preflush was only approximately 43 percent of the originalpermeability.

The second cell was preflus-hed with 4,300 cc. of a 0.2 percent solutionof 'y-aminopropyltriethoxysilane in a mixture consisting of 20 percentisopropanol and 80 percent diesel oil. After the preflush, the retainedpermeability was approximately 94 percent of original permeability; andafter a standard resin treatment, the retained permeability wasapproximately 69 percent of the original permeability. The averagecrushing strength of the treated core was found to be approximately1,736 psi.

No standard resin treatment of the first core was attempted, inasmuch asthe permeability was so low as to render plastic treatment quitedifficult. It may be noted, however, that the core which was preflushedwith a solution containing isopropanol had a permeability even afterplastic treatment which was higher than the permeability of the initialcore before plastic treatment.

The data obtained from the second core when compared with the crushingstrengths observed in previous examples also show that the inclusion ofis-opropano-l has slight, if any, effect on crushing strength.

' The following additional tests were also run which also show theeffectiveness of the plugging retardant in the described process.

Example 4 with a solution made up of 2,0000 parts of isopropan'ol,

8,000 parts of diesel oil, and 5 parts of'y-aminopropyltrieth-oxysilane. The remaining cor'e, Core B, was flushedWith a solution consisting of 10,000 parts diesel oil and 5 partsy-aminopropyltriethoxysilane. The following results were obtained fromCore A:

Volume throughput Percent of the in cc: original flow rate 300 96 Thefollowing results were obtained from Oor'e B:

Example 5 The same general procedure used in conducting the test on CoreA in Example 4 was repeated. However, a number of other pluggingretard-ants were used in the place of isopropanl. The results ar'e shownbelow:

Percent Retained Permeabiltly Volume Solvent Throughout Acetone Ethyleneglycol monobutyl ether flcthoxy ethyl acetate B-methoxy ethyl acetate.Hexanol..- Methyl ethyl ketone From the above data, it may be cleanlyseen that a variety of solvents may be used for reducing the effects ofplugging in the formation consolidating technique taught herein.

Example 6 An additional run was made to further demonstrate theeffectiveness of the present technique for consolidating loosematerials. Prior to the conducting of this experiment, atphenolformaldehyde resin was prepared in the following manner: A firstsolution consisting of 252 grams of 37 percent formaldehyde in a watersolvent, 195 grams of phenol, and 25 grams of a percent sodium hydroxidesolution in a water solvent was mixed together in a 2,000-ml., 3-neckedflask fitted with a stirrer, condenser, and thermometer. The solutionwas heated to 175 F. and held at this temperature for 1 /2 hours. At theexpiration of this time, heat was removed from the flask, and thcsolution was allowed to cool to 107 F. When the solution reached thistemperature, it was neutralized to a pH of about 4-6 with 27 cc. of a 32percent aqueous HCl solution, whereupon the solution separated into twolayers; the top layer was discarded, and the bottom layer was found tohave a volume of about 265 cc. To the bottom layer was added 205 gramsof resorcinol, and the resulting solution was diluted with an equalvolume of ethanol.

A second solution was prepared by mixing together 279 grams of cresol,267 grams of a 37 percent formaldehyde solution in a water solvent, 133grams of parafiormaldehyde, and 17.75 grams of a 50 percent aqueoussodium hydroxide solution. The cresol used consisted of 54 percentmetacresol, 29 percent paracresol, and 17 percent phenol. After mixing,the ingredients were heated to 125 F., and the temperature wasmaintained at this level for 30 minutes. Subsequently, the solution wascooled to about 107 F. and neutralized with percent aqueous HCl to a pHof about 4. At this time no layering was observed in the solution.Subsequently, 17.75 grams of sodium hydroxide were added; and thesolution was again heated to and maintained at 125 F. for an additional15 minutes, whereupon it separated into two layers. As in thepreparation of the first solution, the top layer was discarded; and thelower layer, which was about 382 cc. in volume, was heated to 175 F. forabout 1 /2 hours. The resulting mixture separated into two phases, andthe upper phase was again discarded. The lower layer was diluted with anequal volume of ethanol.

Following the preparation of the two solutions, 33 cc. of the firstsolution and 33 cc. of the second solution were combined with 33 cc. ofethanol and 0.9 cc. of a 25 percent aqueous solution of sodiumhydroxide. After these steps were taken, the resulting mixture was usedin the standard phenol-formaldehyde resin treatment describedpreviously. Results obtained from this experiment are designated Run Abelow.

For Run B, the same procedure was followed except that the core wasgiven a lpreflush prior to the resin treatment with 4,000 cc. of a 0.2percent solution of 'yaminopropyltriethoxysilane in 80 percent dieseloil and per- It will be noted that the results obtained in thisoperation are in favorable agreement with results previously reported.

Example 7 In order to demonstrate the feasibility of including thecoupling agent directly in the resin mixture prior to injection of themixture into the formation, two additional cores of Black Hawk E sandwere prepared as described previously. Into each of the cores was theninjected 100 cc. of a phenol-formaldehyde mixture. This mixture wassubstantially the same as that described previously in the discussion ofthe standard phenolformaldehyde resin treatment. However, instead ofusing 0.9 cc. of a percent aqueous NaOH solution, 1 cc. of'y-aminopropylethoxysilane was preblended with the resin mixture. Afterthis treatment, the cores were cured for four days at 160 F. and werethen found to have a retained permeability of about 85 percent and anaverage crushing strength of about 1,285 psi.

The values obtained from this process compare favorably with thosevalues obtained when the coupling agent was added to the coreseparately.

Example 8 In addition to the methods described above in the generalportion of the specification and demonstrated in the specific examples,there is another technique which may be employed in practicing oneaspect of the present invention. More particularly, it is possible topractice one aspect of this invention by the utilization of a sandphenolformaldehyde resin mixture-coupling agent slurry, usually in a carrierliquid. In practice, the slurry is first mixed at the wellhead and thenpumped downhole where it is placed against the formation surrounding thewellbore or possibly into cracks and fissures in the formation whichcommunicate with the wellbore. Subsequently, the area of the formationsurrounding the wellbore will be maintained in a substantially staticcondition for a :sufficient time to allow the resin to harden. This timewill vary depending upon many factors which characterize both themixture itsel and formation conditions.

I Ordinarily from about 12 to about 48 hours will be adequate.

As in the case when coupling agent and resin mixture are injected intothe formation, there is no criticality attached to the order in whichthe slurry components are added together. Ordinarily it will probably bemost convenient to add the coupling agent directly to the resin mixture.However, satisfactory results will also be obtained when the couplingagent is added to the sand alone, or to a sand-resin mixture slurry. Ingeneral the range of satisfactory ratios between the coupling agent andphenol-formaldehyde resin mixture will be the same as that foundsuitable when the combined resin mixture and coupling agent are injecteddownhole. Similarly, when the coupling agent is introduced to the sandeither before or after the sand is slurried with the phenol-formaldehyderesin mixture, the ratio between coupling agent and carrier will be inthe same range of ratios which may be used when the coupling agent isinjected into a formation as a preflush. The sand to resin mixture ratiois not critical; it only being necessary that there be sufficient resinto substantially completely coat the sand particles.

In general from about 5 to about bulk unit volumes of sand per unitvolume of resin material will be found satisfactory with a preferredrange of from about 16 to 35, although either more or less sand may beused per volume of resin material without unduly limiting the eflicacyof the technique. It is to be understood, of course, that the resinmaterial will ordinarily be in a suitable solvent of which many are wellknown in the art. While the concentration of the resin solution is notcritical, generally the solution will contain at least about 5% resinmaterial when a solvent is used. It will be observed that the same ratiobetween solvent and resin material also applies when the resin materialis injected directly into the formation. Additionally, rhen a carrier isused with the slurry, as it ordinarily will be, the same carriermaterials may be used which were described previously for use with thecoupling agent. Generally the ratio between the coated sand and carrieris not critical although it will ordinarily be in the range of fromabout .1 to about 4 pounds of sand per gallon of carrier with apreferred range of from about .25 to about 1 pound per gallon.

The preferred range of sand sizes is from about 20 to about 40 mesh.Sizes outside this range are allowable, however, and in general, sand aslarge as 4 mesh and as small as 200 mesh may be utilized.

Before considering the specific examples which demonstrate thistechnique, it should be pointed out that the use of a coupling agent inthis embodiment of the invention is a critical part of the process.Absent a coupling agent, the resin mixture will not satisfactorilyadhere to the sand grains during the process. This is true in spite ofthe fact that it has been found to adhere satisfactorily to particulateorganic matter (US. Patent 2,941,594) under similar conditions.

In order to demonstrate the feasibility of this technique, 240 grams of20 to 40 mesh Ottawa sand were stirred into ml. of diesel oil to whichhad been added 0.4 ml. of 'y-aminopropylethoxysilane. After agitation ofthe resulting mixture for approximately two minutes, the coated sand wasthen flushed with about 500 cc. of diesel oil and about 500 cc. ofdiesel oil were then added to the mixture. Subsequently, 50 ml. of analcohol solution containing about 30% of the phenol-formaldehyde resinmixture used in Example 1 was stirred into the sand-diesel oil-couplingagent mixture. Following agitation, the slurry was poured onto a 50 meshscreen and flushed with approximately 500 cc. of diesel oil.

After the slurry was thus prepared, it was introduced into a closedconduit which was approximately 12 feet long and %-inch in diameter. Thetotal capacity of this closed conduit was approximately two liters.After being placed into the conduit, the slurry was pumped around theclosed circuit at the rate of about 15 gallons per minute in order tosimulate the step of pumping the slurry down a tubing string. Afterbeing pumped around the closed conduit for approximately 4 minutes, theslurry was shunted through a screen by which means the coated sand wasrecovered. After recovery of the sand, it was packed into a 'Ms-inchplastic tube and cured at 160 F. After approximately 4 /2 hours curingtime, the sand pack Was found to have an average compressive strength of839 p.s.i. and a permeability of approximately 40 darcies. After curingdays the average crushing strength was found to be about 1,830 p.s.i.

A second experiment was conducted which was similar in concept to theone described immediately above. In this experiment, however, 300 gramsof the sand were introduced directly to the closed conduit before beingcoated with the resin mixture. Subsequently, 50 ml. of solutionconsisting of 30% phenol-formaldehyde resin mixture in alcohol togetherwith 0.5 ml. of -aminopropylethoxysilane was introduced into theapparatus while the pump was running. After about 4 minutes the sand wasremoved and packed as described above.

At the end of 5 days during which time the resincoated sand wasmaintained at 160 F., the sand packs were found to have an averagecrushing strength of about 2093 p.s.i.

From the foregoing description of the invention, it will be appreciatedthat the described process provides certain marked improvements inmethods currently used for consolidating incompetent subterraneanformations. Although certain specific examples have been given, it

'is not intended that the invention be limited to or circumscribed bythe specific details of material, proportions, or conditions hereinspecified, since such materials, proportions and conditions may bevaried or modified according to individual preference without operatingoutside the broad principle underlying the invention. For example,instead of using phenol form-aldehyde as the resinous material toconsolidate the formation or slurry with sand, other condensationproducts of water-soluble aldehydes and low molecular weighthydroxylaryl compounds may be used. Also a Wide variety of the Wernercomplex-type compounds may be used as coupling agents as may numerousaminoorganosilanes. Moreover, numerous compounds other than thosedisclosed in the specific examples may be chosen to work effectively asa plugging retardant. Selection of specific compositions and thequantity thereof to be used will, as has been indicated, depend upon theproblems posed by the particular formation which is to be consolidated.

Having fully described and illustrated the practice of the presentinvention, what we desire to claim as new and useful and to secure byLetters Patent is:

1. In the method for consolidating an incompetent subterranean formationcontaining siliceous material in an amount suflicient to react with afunctional group of coupling agent which method comprises injecting intothe formation an age-hardenable resinous composition, the improvementwhich comprises injecting into the formation prior to the injection ofsaid age-hardenable composition a plugging retardant and a couplingagent for chemically bonding said age-hardenable composition to theformation, said coupling agent comprising a chemical compound containinga first functional group which reacts with the particles of theformation and a second functional group which reacts with theage-hardenable composition whereby the consolidation of said formationis improved.

2. The method defined in claim 1 wherein said plugging retardant ischosen from the group consisting of alcohols, ketones, and esters.

3. The method defined in claim 1 wherein said plugging retardant isacetone.

4. The method defined in claim lwherein said plugging retardant isisopropanol.

5. In the method for consolidating an incompetent subterranean formationwhich comprises injecting into the formation an age-hardenable resinouscomposition, the improvement which comprises injecting into theformation prior to the injection of said age-hardenable composition aplugging retardant and a coupling agent for chemically bonding saidage-hardenable composition to the formation, said coupling agentcomprising a compound selected from the group consisting of multivalenttransition metal complexes in which the metal atom is coordinated withan acyclic ca-rboxylic acido group and aminoalkylethoxysilanes in whichthe amino group is attached to a carbon atom of the alkyl group, whichcarbon atom is located no closer to the silicon atom than the gammaposition.

6. The method of claim 5 wherein said age-hardenable resinouscomposition is a phenol-formaldehyde resin.

7. The method of claim 6 wherein said coupling agent is selected fromthe group consisting of gamma-aminopropyltriethoxylsilane andfi-aminobutylmethyldiethoxysilane.

8. The method of claim 7 wherein said plugging retardant is isopropanol.

9. The method of claim 6 wherein said coupling agent comprisesmethacrylato ohromic chloride.

10. The method of claim 9 wherein said plugging retardant isisopropanol.

11. In the method for consolidating an incompetent subterraneanformation which comprises injecting into the formation an age-hardenableresinous composition, the improvement which comprises injecting into theformation prior to the injection of said age-hardenable composition aplugging retardant and a coupling agent for chemically bonding saidage-hardenable composition to the formation, said coupling agentcomprising a compound of the Werner complex type in which themultivalent nuclear metal of the complex is selected from the groupconsisting of chromium, cobalt, nickel, and zinc and in which the acidogroup, which is co-ordinated with the metal atom of the complex, isselected from the group consisting of acrylato and substituted acrylategroups.

References Cited by the Examiner UNITED STATES PATENTS 2,378,817 6/1945Wrightsman et al. 166-33 2,611,718 9/1952 Steinman 117-22 2,674,3224/1954 Cardwell 166.33 X 2,823,753 2/1958 Henderson et al. 16633 X3,052,583 9/ 1962 Carlstrom et al. 26038 X OTHER REFERENCES Spain, H.H.: New Plastic Checks Sand Production, pp. 112-115, in The Oil and GasJournal.

CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN HERSH, Examiner.

T. A. ZALENSKI, S. I. NOVOSAD,

Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,282,338 November 1, 1966 Herbert C. Walther et al.

It is hereby certified that error a ent requiring correction and thatthe s corrected below.

Column 3, line 25, for "incompentent" read incompetent line 59, for "at"read is column 9, line 29, for "speed" read spread column 12, line 6 for"incomponent" read incompetent column 13, line 74, for "2,0000" read2,000 column 14, line 31, for "isopropanl" same column 14, in the secondtable,

read isopropanol first column, line 4 thereof, for "acetate" readacetane Signed and sealed this 5th day of September 1967.

( AL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner ofPatents ;g UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PatentNo. 5,2 2,33 Dated November 1, 9 0

InventO (S) Herbert C. Walther, David A. Kuhn and Derry D. Sparlin rorappears in the above-identified patent It is certified that er arehereby corrected as shown below:

and that said Letters Patent Column 12, line 2, "2,981,354" should read2, 23,753

SIGNED A'N'D SEALED JUN 9 197g fi Arum:

EdwardM. Fletcher, In

WILLIAM E. 50mm. JR. Attesnng Officcr Commissioner of Patents

1. IN THE METHOD FOR CONSOLIDATING AN INCOMPETENT SUBTERRANEAN FORMATION CONTAINING SILICEOUS MATERIAL IN AN AMOUNT SUFFICIENT TO REACT WITH A FUNCTIONAL GROUP OF COUPLING AGENT WHICH METHOD COMPRISES INJECTING INTO THE FORMATION AN AGE-HARDENABLE RESINOUS COMPOSITION, THE IMPROVEMENT WHICH COMPRISES INJECTING INTO THE FORMATION PRIOR TO THE INJECTION OF SAID AGE-HARDENABLE COMPOSITION A PLUGGING RETARDANT AND A COUPLING AGENT FOR CHEMICALLY BONDING SAID AGE-HARDENABLE COMPOSITION TO THE FORMATION, SAID COUPLING AGENT COMPRISING A CHEMICAL COMPOUND CONTAINING A FIRST FUNCTIONAL GROUP WHICH REACTS WITH THE PARTICLES OF THE FORMATION AND A SECOND FUNCTIONAL GROUP WHICH REACTS WITH THE AGE-HARDENABLE COMPOSITION WHEREBY THE CONSOLIDATION OF SAID FORMATION IS IMPROVED. 